answer file of type "JPEG"

Hi listers,
has anyone successfully used e.g.:
answer file "yadda" of type "JPEG"
on OS X?
Does not work, not ALL jpgs are shown in the open-dialog...
Some are dimmed...
Looks like the ones (coming from win or a digital camera!) without a
"filetype" are dimmed.
Their last item is empty in the "long files"...
Is it a bug?
Is it already bugzilla'd?
Are there (not too ugly ;-) workarounds?
I reported this yesterday:
[Bug 762] result is empty when setting the filename of an image to a
non-image file!
So checking the result does not work in this context/case...
Thanks in advance...
Regards
Klaus Major
klaus at major-k.de
www.major-k.de